Minimally-invasive intracardiac ablation is the treatment of choice for various types of arrhythmias. To perform such treatment, the physician typically inserts a catheter through the vascular system into the heart, brings the distal end of the catheter into contact with myocardial tissue in areas of abnormal electrical activity, and then energizes one or more electrodes at or near the distal end in order to create tissue necrosis.
Various methods for monitoring ablation treatments are known in the art. For example, U.S. Pat. No. 7,001,383, whose disclosure is incorporated herein by reference, describes real-time monitoring and mapping of ablation lesion formation in the heart. The disclosed method includes applying a local treatment to the heart at a plurality of sites designated for ablation. At each respective site, a parameter is sensed that is indicative of a level of ablation at the site. The method preferably includes displaying a map of the heart, and designating, on the map, during the ablation procedure, indications of the respective levels of ablation at the sites, responsive to the respective sensed parameters.
U.S. Patent Application Publication 2014/0171936, whose disclosure is incorporated herein by reference, describes a catheter having an irrigated tip with temperature sensors and an optical fiber array. The catheter comprises an insertion tube having a distal end configured for insertion into proximity with tissue in a body of a patient and containing a lumen having an electrical conductor for conveying electrical energy to the tissue. A conductive cap is attached to the distal end of the insertion tube and is coupled electrically to the electrical conductor. A multiplicity of optical fibers are contained within the insertion tube, each fiber terminating in proximity to the outer surface of the cap, and being configured to convey optical radiation to and from the tissue while the electrical energy is being conveyed to the tissue.
U.S. Pat. No. 8,147,484 describes a system and method that enable real-time optical measurements of tissue reflection spectral characteristics while performing ablation. The method involves the radiation of tissue and recapturing of light from the tissue to monitor changes in the reflected optical intensity as an indicator of steam formation in the tissue for prevention of steam pop. The system includes a catheter adapted to collect light reflected from tissue undergoing ablation, a detection component that identifies and separates constituent wavelengths of collected light, a quantification apparatus for generating measured light intensity data for the collected light, and a processor that analyzes the measured light intensity data in relation to time. A measured reflectance spectral intensity (MRSI) versus time is analyzed, wherein observation is made as to whether the MRSI initially increases in a specified time period followed by a decrease at a specified rate in the MRSI. If there is no decrease in the MRSI, then delivery of ablation energy to tissue continues. However, if there is a decrease in the MRSI within a specified time and at a specified rate, then the method infers the formation of a steam pocket and decreases or discontinues the delivery of ablative energy to tissue.
Documents incorporated by reference in the present patent application are to be considered an integral part of the application except that to the extent any terms are defined in these incorporated documents in a manner that conflicts with the definitions made explicitly or implicitly in the present specification, only the definitions in the present specification should be considered.